Tumbling of workpieces

ABSTRACT

A shot blasting apparatus in which abrasive shot is impelled at workpieces held for tumbling action within a rotating container of perforate outer wall construction and having perforate internal wall construction dividing the interior of the container into sectors allowing separate tumbling of different types of workpieces. One embodiment shows arrangements for conveniently changing compartment arrangements within the container.

United States Patent [191 Walker 1 1 Feb. 27, 1973 TUMBLING 0F WORKPIECES 1,491,601 4 1924 Fuller .5l/l64 2,565,341 8/1951 Arispe [76] Inventor: Helen H. Walker, 607 Charlton Street valdosta, Ga- 2,752,732 7/1956 Walker ..5 1/13 X [22] Filed: May 10, 1971 Primary Examiner-Donald G. Kelly N0: Brunet Related US. Application Data [57] ABSTRACT [63] f 6 of May A shot blasting apparatus in which abrasive shot is iman one pelled at workpieces held for tumbling action within a LS. 51/13 rotating container of perforate uter wall construction [51] Int. Cl ..B24c 3/30 and having perforate internal wall construction dividnew of Search "51/9, 15, 164; 241/137 ing the interior of the container into sectors allowing separate tumbling of different types of workpieces. [56] References cued One embodiment shows arrangements for con UNITED STATES PATENTS veniently changing compartment arrangements within the container. 3,148,485 9/1954 Garvey ..5l/13 X 3,540,155 11/ 1970 Walker ..51/9 20 Claims, 6 Drawing Figures 3,546,816 12/1970 Enegren ..51/l3 2,884,209 4/1959 Bargero ......241/137 X 2,013,179 9/1935 Gerasch ..241/137 X 24 92 ==L-' \& 6o 5 Z6 74 f 4 t o= Z 1.. g5

4b I04 b PATENTEDFEBZTIQH 3717,

sum 10F 3 INVENTOR.

Hem M PATENTED FEB 2 7 I975 SHEET 2 OF 3 INVENTOR. HEW/Y Mme/e PATENTEDFEBZYIW 3,71% 957 SHEET 3 0F 5 INVE/N'TOR. Has/v H Mwee TUMBLING F WORKPIECES This invention relates to the treatment of workpieces and more particularly, it concerns novel workpiece tumbling arrangements to be employed in conjunction with spray working of such workpieces.

Spray working involves the exposure of a workpiece to the action of a high velocity fluid or semi-fluid medium whereby the surface of the workpiece becomes abraded, cleaned or otherwise treated by the action of the medium against its surface. Many types of medium may be used, for example detergents, etchants, coating compounds, etc. A particularly prominent form of spray working involves the use of an abrasive powder which is blasted against the workpiece and abrades away the surface of the workpiece to clean it or smooth it. In the trade, such operations are known as shot blasting or sand blasting. For purposes of illustration, and because of its particular suitability to sand blasting arrangements, the present invention will be described in connection with such arrangements.

In order to obtain uniform treatment about the surface of a workpiece, it is important that the workpiece be turned continually with respect to the direction of impingement of the working spray. In the past, workpiece tumbling baskets have been used to obtain simultaneous treatment of several workpieces in a single operation. These workpiece baskets were in the form of closed containers having walls of perforate construction for allowing admission of the working spray into their interior. A door was provided on the container for placing the workpieces therein and retrieving them after processing. Several such workpieces were placed together in the container and then the container was rotated in the path of the working spray while the workpieces tumbled inside the container. This served to provide random, yet uniform, exposure of all workpiece surfaces to the working spray.

An example of a workpiece tumbling container used in conjunction with an abrasive shot spray produced by rotating paddle wheels is shown and described in copending application Ser. No. 623,418 filed Mar. 15, 1967, now US. Pat. No. 3,540,155, dated Nov. 17, I970.

The present invention provides improved workpiece tumbling arrangements for use in spray working apparatus. According to one feature of the present invention, several workpieces of widely differing weight, size, hardness, etc. can be tumbled simultaneously in the same working spray without adverse effects. In the past, the larger, heavier (and often harder) workpieces, when tumbled with small, lighter or softer workpieces, would either cause direct damage to the latter or they would shield the latter from full exposure to the working spray. This problem could not be overcome by holding or clamping the workpieces inside the container because any such holding or clamping means would mask a portion of each workpiece from the working spray. Also, it is necessary that the workpieces tumble inside the container to prevent masking by the outer walls of the container.

The present invention overcomes these difficulties of the prior art by providing a tumbling container having an outer wall of perforate construction for admitting a working spray into the interior of the container and inner partition walls, also of perforate construction,

separating the interior of the container into compartments in each of which a different one or group of workpieces is tumbled. The outer wall is provided with separate doors opening to each compartment for loading and unloading the various workpieces.

The compartmentalized workpiece container is rotated in the path of a working spray so that the workpieces can tumble therein. The inner partition walls, however, permit substantially free passage of the working spray to act upon all surfaces of each workpiece. At the same time, however, the workpieces in the different compartments are held in isolation from each other so that damage to the softer or smaller workpieces is avoided.

Various further and more specific objects, features and advantages of the invention will appear from the description given bleow, taken in connection with the accompanying drawings, illustrating by way of example preferred forms of the invention.

In the drawings:

FIG. 1 is a side elevational view, partially in section of a shot blasting machine in which the present invention is embodied;

FIG. 2 is a fragmentary front elevational view, also in section of the shot blasting machine of FIG. 1;

FIG. 3 is a perspective view of a workpiece container used in the shot blasting machine of FIGS. 1 and 2;

FIG. 4 is a fragmentary front elevational view of an alternate workpiece container in which the present invention is embodied;

FIG. 5 isa view taken along line 5- -5 of FIG. 4 when compartment defining bars or rods are not in place; and

FIG. 6 is a view similar to FIG. 5 showing an arrangement of compartment defining bars or rods.

As shown in FIGS. 1 and 2, the shot blasting machine in which the present invention is embodied comprises an outer housing 10 within which is located a lower impeller l2 and an upper workpiece container 14.

The housing 10 is made up of front, rear and top walls l6, l8 and 20 (FIG. 1), and a pair of sidewalls 22 (FIG. 2). These walls define an enclosure 24 within which the workpiece container 14 is located. As shown in FIG. 1, the front wall 16 is provided with a door 26 which provides access to the workpiece container.

The impeller 12 comprises a plurality of flat blades 28 extending radially from a horizontal axle 30. The axle, in turn, is supported for rotation in bearings 32 mounted toward the bottom of the housing 10 beneath the workpiece container 14. The axle is provided at one end with a pulley 34 and a drive belt 36 extends from the pulley to the drive shaft of an impeller drive motor 38. As can be seen, the motor 38 causes the impeller 12 to spin about its axle 30.

The impeller 12 is situated within an impeller casing 40 located centrally of the bottom region of the housing 10. The casing 10 opens upwardly into hopper walls 42 (FIG. 1) and 44 (FIG. 2) which flare out to meet the front, rear and sidewalls 16, 18 and 22 of the housing 10 just below the workpiece container 14. The hopper walls serve to catch spent abrasive shot which falls from the workpiece container and the upper regions of the housing 10. This shot collects near the bottom of the hopper walls and is directed, by means of chute elements 46, onto the impeller 12 near its axle 30. As the impeller spins, its blades 28 fling the shot up toward the workpiece container 14.

The workpiece container, which is best shown in FIG. 3, is essentially a cylindrical basket of open metalwork construction. It comprises a pair of metal disks 50 forming the ends thereof; and these disks are interconnected by means of a plurality of parallel rods 52 secured to and extending between corresponding points about the periphery of each disk. A perforate outer wall 54 covering of expanded metal or metal mesh construction extends about the rods 52 to provide an enclosed container. In situations where large size workpieces are to be processed and in situations where the rods 52 are sufficiently closed to each other to prevent the workpieces from passing or wedging between them, the rods themselves may constitute the perforate outer wall covering and the expanded metal or metal mesh may be dispensed with.

A number of inner rods 56 similar to the outer wall forming rods 52 extend between corresponding locations on the disks 50 along lines which extend radially from the centers of the disks to their periphery. These inner rods lie in radially extending planes and divide the workpiece container 14 into sectors or quadrants 58 (FIG. 1).

As can be seen in FIGS. 1 and 3, perforate divider walls 60 of expanded metal, wire mesh, or the like are secured to extend along the planes defined by the inner rods 56. Again, where the rods 56 are close enough together in relation to the size of the workpieces, the rods 56 themselves may constitute the divider walls and the expanded metal, etc., may be eliminated.

Each of the sectors or quadrants 58 is provided with a special door 62 (FIG. 3). As shown in FIG. 3, this door extends between the disks 50 and between adjacent ones of the outer wall forming rods 56. The doors 62 each comprise a pair of flat end pieces 64 shaped as circular segments and interconnected by means of door-forming rods 66 which extend along parallel to the outer wall forming rods 52. A perforate door wall covering similar to the outer wall covering 54 may be provided to extend over the rods 66.

The segmental end pieces 64 are pivoted at one end to the opposite ends of one of the rods 66. The other ends of the end pieces 64 are notched, as at 68, to rest against the next adjacent rod 52 when the door is closed. In the closed position of the doors 62, the segmental end pieces 64 lie adjacent and contiguous with the disks 50; and the door forming rods 66 and covering 68 extend in the same cylindrical plane as the outer wall forming rods 52 and the wall covering 54. The doors are held in closed position by means of inwardly protruding lugs 70 which pass through openings 72 in the disks 50 and door openings 73 in the end pieces 64 near their free ends. The lugs 70 are attached to locking strips 74 of spring steel attached to the outside of the disks 50. To unlock and open one of the doors 62, a handle extension 76 of the locking strips 74 on the opposite ends of the door is pulled outwardly to retract the lugs 70 from the door openings 72. The door now may be swung open, as illustrated in FIG. 3. Workpieces can be removed from the container sector into which the particular door 62 opens; and new workpieces can be positioned in the sector. The door 62 is closed and locked by bringing the door openings 73 into alignment with the disk openings 72 and then passing the lugs 70 through the aligned openings. The resilience of the locking strips 74 serve to hold the lugs in place. It will be appreciated that the doors can be individually and independently opened and closed to provide separate access to each chamber or sector of the workpiece container.

The disks 50, as shown in FIGS. 2 and 3, are each provided with a flange coupling 80 at the center of their outer surface and an axle 82 extends outwardly form each coupling. The axles 82 pass through openings in the sidewalls 22 of the outer housing 10 and are mounted for rotation in bearings 86 outside the housing. As shown in FIGS. 1 and 2, a drive sprocket 88 is attached to one of the axles and a driver chain 90 (shown in dotted outline in FIG. 1) extends from the sprocket 88 to a container drive motor 92.

A dust disposal system comprising a cyclone tank 94 having an air lock 95, also driven by the motor 92, is provided outside the housing 10. The cyclone tank has an inlet conduit 96 for receiving dust and shot from he upper regions of the housing 10, a return conduit 98 for returning heavier reusable shot from the air lock to the housing 10 just above the hopper walls 42 and 44, and an exhaust conduit 100 through which unusable fine dust passes to a dust collector 102. A fan 104 in the exhaust conduit 100 serves to maintain proper air flow through the dust disposal system.

In operation of the system, different workpieces of different sizes and weights are placed within the different container sectors according to the sizes and weights of the workpieces. The unit is then put into operation with the impeller 12 spinning to throw shot up into and through the walls of the workpiece container while the container revolves slowly to tumble the workpieces and expose all of the surfaces thereof to the abrasive action of the shot. It will be appreciated that the shot finds its way into all of the sectors of the container to contact the various surfaces of the workpieces as the container turns about the axles 82. The workpieces in each sector tumble as the container turns; however, the heavier workpieces in one sector are prevented by the sector walls from impinging upon and damaging the lighter and smaller workpieces in another sector. At the same time, a proper tumbling action of all the workpieces is maintained. It will also be appreciated that the workpieces in the different sectors can be separately loaded and unloaded so that different types of workpieces can be processed in the unit for different lengths of time and yet the processing of the various different workpiece elements can be undertaken simultaneously.

It will be noted that the workpiece container 14 is rotatably mounted in a position such that the several doors 62 thereof successively come into registry with the access or outer housing door 26. This permits convenient loading and unloading of workpieces in each of the several compartment of the container.

FIGS. 46 illustrate another form of workpiece container according to the present invention. As can be seen in FIG. 4, there are provided a pair of disk-like end plates and 11 arranged parallel to each other in spaced apart relationship and in axial alignment the sidewalls 22 of the housing 10. Each end plate is provided with an outwardly extending axle 112 which passes through the adjacent sidewall 22 and is journalled in a bearing 114 mounted outside the sidewall. A plurality of rods or bars 1 16 extend in parallel relation- PATENTED FEB 2 71975 SHEET 3 or 5 INVE/N'TOR. Has/v H Mweg 

1. A shot blasting apparatus comprising a closeable housing, abrasive shot impeller means arranged in the interior of the housing, hopper means arranged about the impeller means to collect falling abrasive shot a workpiece tumbling container mounted for rotation within the housing in the path of shot blast from the impeller, said container comprising a perforate peripheral outer wall and a plurality of radially extending perforate inner walls dividing the interior of the container into a plurality of compartments each including as one wall thereof a portion of said outer wall and a plurality of door means formed in the different portions of said outer wall.
 2. A shot blasting apparatus according to claim 8 wherein said container comprises a pair of end plates separated by a plurality of parallel bars extending between corresponding points about the peripheries of the end plates to form a closed container of perforate construction, and wherein said door means is arranged on the container between the end plates and between adjacent ones of said parallel bars at each compartment, said dooR means also being of perforate construction.
 3. Workpiece tumbling apparatus according to claim 2, wherein said partition walls also comprise closely spaced bars extending between said end plates along lines thereon extending from their periphery to their center.
 4. Workpiece tumbling apparatus according to claim 2, wherein said door means each comprise end plate segments pivotally connected at one end to corresponding points on said end plates near the periphery thereof and interconnected by bars which extend between corresponding points on said end plate segments.
 5. Workpiece tumbling apparatus according to claim 2, wherein a perforate metal sheet is secured along each of the planes defined by the bars extending between the end plates.
 6. A shot blasting apparatus according to claim 5 wherein said abrasive shot impeller means comprises a paddle-type impeller arranged to spin near the bottom of the interior of the housing and wherein said housing means is arranged above the impeller means to direct downwardly falling abrasive shot into the path of impeller movement.
 7. A shot blasting apparatus according to claim 1, wherein said outer housing is formed with an access door and wherein said workpiece container is rotatably mounted in a position such that said door means successively come into registry with said access door.
 8. A workpiece tumbling apparatus according to claim 2, wherein at least some of said bars are removable from between said end plates.
 9. A workpiece tumbling apparatus according to claim 8, wherein at least some of the removable bars are among those extending between corresponding points about the peripheries of the end plates, thereby to form said door means.
 10. A workpiece tumbling apparatus according to claim 8, wherein at least some of the removable bars are among said closely spaced bars which form said partition walls.
 11. A workpiece tumbling apparatus according to claim 8, wherein said end plates are formed with a plurality of removable bar attachment means at multiple locations distributed about said end plates for permitting formation of different compartment arrangements in said workpiece tumbling apparatus.
 12. A workpiece tumbling apparatus according to claim 8, wherein said bars are temporarily secured to said end plates by resilient means.
 13. A workpiece tumbling apparatus according to claim 8, wherein said bars extend into holes in said end plates.
 14. A workpiece tumbling apparatus according to claim 13, wherein at least one end plate has an opening therethrough at each location for inserting a bar, the other end plate having means at each corresponding location permitting partial insertion of the end of each bar, and said one end plate having movable means for preventing retraction of an inserted bar.
 15. A workpiece tumbling apparatus according to claim 14, wherein each holding means is a leaf spring mounted on the outside surface of said one plate.
 16. A workpiece tumbling apparatus according to claim 2, wherein said partition walls are arranged to define a compartment coaxial with respect to outer perimeter of said tumbling apparatus.
 17. A workpiece tumbling apparatus according to claim 2, wherein said outer perimeter of said tumbling apparatus is cylindrical.
 18. A workpiece tumbling apparatus according to claim 2, wherein said partition walls define an inner cylindrical compartment within said outer perimeter.
 19. A workpiece tumbling apparatus according to claim 1, wherein at least some of said inner walls extend in radial planes to divide the container into longitudinally arranged compartments.
 20. a workpiece tumbling apparatus according to claim 3, wherein at least some of said partition walls are formed by a mesh connected between said bars. 